Development and Validation of a Vibration-Based Virtual Sensor for Real-Time Monitoring NO x Emissions of a Diesel Engine.

With a strong legal basis and regulatory authority, cost-effective transient emission sensors that reflect real-driving emissions are key factors for accomplishing environmental requirements. It is difficult for the existing NO_x emission monitoring techniques to achieve a balance between accuracy and timeliness. Fundamentally, in-cylinder combustion is the thermodynamic cause of NO_x emissions and the main excitation source for engine vibration and noise emissions. A novel vibration-based virtual NO_x sensor is developed based on these critical relationships for real-time NO_x monitoring. First, the correlation between vibration and NO_x emission was characterized in-depth. Then, a technique of constructing two-dimensional filters for vibration signals is proposed to extract combustion-related information. A principal component regression (PCR) model for NO_x prediction was established based on the reconstructed in-cylinder pressure. Finally, the virtual NO_x sensor is tested and validated on a single-cylinder diesel engine bench. The virtual NO_x sensor is proven to meet the accuracy requirement of vehicle emission monitoring for both steady-state and transient conditions and has a better frequency response compared to the emission measurement system. [ABSTRACT FROM AUTHOR]